This is a most delicious sauce, very easy to make, if care is taken to observe every minute detail given in the directions for making it. Mayonnaise sauce is simply yolk of egg and oil beaten to a butter. This butter is only formed under the following circumstances. First, the oil must not be warm, and yet it must be bright and not at all frozen. If in summer, therefore, it will be well to stand the bottle of oil in some cold spring water, or some water with a piece of ice in it, for about half an hour. If in winter, and the oil is cloudy, place the bottle in lukewarm water till the oil becomes perfectly bright, but be careful not to let it get too warm. Next, take a basin, and break an egg, carefully separating the yolk from the white. (See No. 15.) Get rid of all the white, and place the yolk in the basin, break it, and remove the thread that very likely will cling to it. Next, beat up the yolk with a fork, and drop some oil on it drop by drop, very slowly at first. Gradually it will become thicker and thicker, as more oil is added. When it gets fairly thick you can add the oil a teaspoonful, or even more, at a time, but you must keep beating.

Recollect, to get mayonnaise sauce really thick like butter, you must add plenty of oil and beat it up patiently. "When it is as thick as ordinary fresh butter on a summer's day it is finished. Mayonnaise sauce is flavoured with pepper and salt and vinegar. The pepper should be white, and so also the vinegar. As mayonnaise sauce is generally required to mask over surfaces, it is desirable to have it as thick as possible. Instead, therefore of adding ordinary vinegar to give it a slight acidity, get some concentrated vinegar at the chemists in the form of dilute acetic acid. Half a teaspoonful of this is equal to a tablespoonful of vinegar, yet you have the slight acid flavour without making the sauce thin. The common cause of failure in making mayonnaise sauce is - first, that English cooks think it should be liquid instead of a solid. Secondly: they put the salt and pepper in at starting, or else add vinegar and oil alternately. The mayonnaise sauce made this way is more of a salad dressing than real mayonnaise.